This invention relates to an apparatus for measuring the thickness of a running sliver bundle in a drawing frame. A sliver guide is arranged at the inlet of the drawing unit of the drawing frame for the sliver bundle which is composed of side-by-side inputted slivers. The slivers are guided in a single plane through a measuring member which includes a biased, movable, mechanically contacting sensor element which, in cooperation with a counterface, forms a constriction through which the slivers pass after being densified thereby. The positional changes of the sensor element in response to thickness fluctuations of the running sliver bundle formed of the slivers are converted into electric control pulses by a transducer.
According to a known device which measures the thickness of a sliver bundle and which includes a sliver guide for guiding the sliver bundle at the drawing unit inlet, the walls of the device converge at least partially conically to gather the slivers inputted in one plane. Further, a roll pair is arranged downstream of the sliver guide. The slivers again diverge downstream of the roll pair. The sliver thickness measuring device has a biased, movable sensor element which forms a constriction with a stationary counterface for the throughgoing sliver bundle as outlined above. The sliver thickness is sensed as the densified slivers are guided in the sliver guide side-by-side, while the roll pair withdraws the sensed slivers.
It has further been proposed to densify the side-by-side arranged slivers from above across the width of the sliver bundle. For this purpose the sensor element, in addition to a sensing and densifying motion in the direction of the slivers, also executes a pivotal motion about an axis which is parallel to the running direction of the slivers and thus the sensor element is able to detect that, for example, slivers of unlike thickness are arranged side-by-side. The movable sensor element has a slide face by means of which the slivers are, in their side-by-side relationship, densified and pressed against the stationary counterface. Disadvantageously, in such an arrangement the thickest sliver determines the distance between the sensor element and the counterface, and even a small thickened location in one of the slivers results in a greater distance. The slivers on either side of such a thickened location are thus pulled out of the thus-obtained clearance without having been submitted to thickness sensing.